I had this problem, called Samsung and was told that the fridge was out of warranty and that the only thing they would do is give me the service centre number.
In the end I decided to do the job myself.
I unscrewed the top panel, starting with the top screw, and then two more lower down.
Then I removed the bottom panel, which has six screws, two behind the removable panels, two holding onto a piece of plastic piping andd two right at the bottom.
The panels were held in by clips which were slightly difficult to release.
Then I unplugged the fan assembly - two plugs, bottom one was blue - and removed the entire bottom assembly.
I then unscrewed the fan assembly from the polystyrene four screws, one hiding behind some metal attachment.
It was ten possible to see the ice build up and defrost it, and enlarge the drain hole.
james r, August 2012